1. Field of the Invention
The present invention relates to a traveling apparatus which can travel on the flat ground and travel up and down on the stairs, a follow-up control method applied when an operator controls the traveling apparatus, and a rotational-angle detecting apparatus used in controlling the traveling apparatus.
2. Related Background Art
An example of conventional traveling apparatus of this type is one as described in Japanese Laid-open Patent Application No. 56-138071, which is shown in FIG. 1. The apparatus is so arranged that four independently driven crawler units 12.sub.1 thru 12.sub.4 are set at the four corners of main body 10 so as to swing about respective fulcrums at one ends 14.sub.1 thru 14.sub.4 independently of each other whereby the apparatus can take various postures. Another example is one as described in Japanese Laid-open Patent Application No. 58-167262, which is shown in FIG. 2. In the apparatus arms 18.sub.1, 182 with auxiliary wheels 16.sub.1, 16.sub.2 at the distal end are rotated to change the shape of crawlers so as to enhance the traveling properties on the stairs. A further example is one as described in Japanese Laid-open Patent Application No. 3-279087, which is shown in FIG. 3. In the apparatus four crawler units 20.sub.1 thru 20.sub.4 are so set as to rotate or swing about respective fulcrums at central portions 22.sub.1 thru 22.sub.4 and a plurality of motors are provided to drive and swing the crawler units 20.sub.1 thru 20.sub.4. Another example of a combination of crawler units and wheels is one as described in Japanese Laid-open Patent Application No. 60-85083, which is shown in FIG. 4. In the apparatus traveling wheels 28.sub.1, 28.sub.2 having up-and-down mechanisms 26.sub.1, 26.sub.2 are given in addition to crawlers 24 whereby the apparatus can travel on the stairs and can travel at high speed on the flat ground.
The conventional traveling apparatus had, however, the following problems. The example of FIG. 1 requires a great deal of skill in handling to change the posture of crawler units 12.sub.1 thru 12.sub.4 in accordance with the road conditions. The example of FIG. 2 requires a complex control to change the posture. Further, the example of FIG. 3 needs a lot of motors for crawler units 20.sub.1 thru 20.sub.4, which makes the structure complex. In addition, these three examples had the problem that the traveling speed was slower on the flat ground because of the drive of crawlers as compared with the wheel traveling, which lowered the energy efficiency. The example of FIG. 4 has the traveling wheels 28.sub.1, 28.sub.2, but is provided with only a pair of crawlers 24 fixed on the body. This arrangement brings a drawback that shock cannot be avoided upon sudden forward inclination at the start of descending stairs or at the end of ascending stairs.